Articles 15

CTA Heliconair HC-I, -II Convertiplano

Brazil’s first foray into jet aircraft started in about 1950 with the arrival of Dr. Heinrich Focke, formerly of Focke-Wulf Flugzeugbau AG in Germany, and his founding of the Centro Técnico Aeroespacial (CTA) in Brazil.

Model and photograph by Zane R Nobbs

Boxart design by Zane R Nobbs and Daniel Uhr

With Professor Focke’s background well established in lifting bodies, such as auto-gyros like the German-built, licensed version of the La Cierva C-19 (Azur Models 1/72) and C-30 (Azur Models 1/72), he moved on to helicopters including: the Fw-61 (Fiddlers Green 1/72) then the huge Focke-Achgelis series Fa-223 Drache "Dragon" (HUMA MODELL 1/72), Fa-224, Fa-266, Fa-269 (RS Models 1/72), Fa-283, Fa-284 (Unicraft Models 1/72) and Fa-336 (Unicraft Models 1/72). He also designed a flying kite, the Fa-330 (PavlaModels 1/72) and converted an Fw-190 piston-engined fighter into a jet aircraft using his own designed Fw-T1 centrifugal turbojet (VAMI Models 1/72).

Drawing supplied by Comando-Geral de Tecnologia Aerospacial - CTA

His German designs culminated with the Fw-Rochen "Sting Ray" (Unicraft Models,VAMI Models1/72) which was a VTOL aircraft powered by the same Fw-T1 driving two counter-rotating propeller blades in the center of the aircraft. The war ended before this design advanced beyond the wind-tunnel models and a 2/3 scale test aircraft.

Photograph supplied by Comando-Geral de Tecnologia Aerospacial - CTA

Naturally, by the time he reached Brazil, Dr. Focke’s focus continued to be on VTOL aircraft. He found a more-than-willing government in Brazil under the leadership of General Eurico Gaspar Dutra, the former commander of the Brazilian Expeditionary Force, which fought in Europe during the Second World War on the Allied side. Coincidentally, this was the same period that Dr. Kurt Tank, also from Focke-Wulf, was helping Argentina build and fly the Instituto Aeronautica I.Ae.33 Pulqui II "Arrow" (RD Resins, Sur Models, Classic Planes 1/72), under General Peron and Willie Messerschmitt was working in Spain on the Hispano Aviacion Ha-200 Saeta "Thunderbolt" (MPMLtd. Models, specialhobby 1/72), for General Franco.

Photograph supplied by Comando-Geral de Tecnologia Aerospacial - CTA

As resources for such a project were meager at best, Dr. Focke decided to utilize a Supermarine Spitfire Mk. XIV (Sword and Academy 1/72) airframe sent to Brazil as a sales demonstration aircraft by Great Britain. Using the wings and airframe, he modified it to accept the Armstrong Siddeley Double Mamba gas-turbine engine. For VTOL he attached four small wings driving counter-rotating propellers on each side. One set was forward of the cockpit with the second set just behind the wings. The tail-planes were also raised to the top of the tail fin to insure stability and steer clear of the exhaust.

Graphics by Zane R Nobbs based on CTA drawing

At that time the United Kingdom decided to stop supplying the Double Mamba to Brazil. With a Labor government in power, it may have been due to Brazil’s right-of-center leadership by the Social Democratic Party-PSD. (Yet during this same period the United Kingdom did supply Argentina, a fascist state, and the Soviet Union, a socialist state, with the Rolls-Royce Nene II.) With this development Dr. Tank hurriedly redesigned the airframe to accept a Wright R-3350-DA3 Turbo Compound 18-cylinder supercharged radial engine taken from a Lockheed Super Constellation, just behind the cockpit. Of course with this revision the passenger/payload compartment was removed and the airframe proved too heavy. This was mainly because the original jet engine was about 700 lbs. or 320 kgs. and the piston engine over 2,670 lbs. or 1,212 kgs.

Graphics by Zane R Nobbs based on CTA drawing

Finally arrangements were made with the U.S.A. to obtain the General Electric G.E. T-58 gas-turbine jet engine. Since this engine weighed only 250 lbs. or 110 kgs., the original layout, with the passenger compartment, was restored with a new designation of HC-II. Four engines were attached, one for each turboprop. Combined engine weight was 1,000 lbs. or about 450 kgs., less than 50% of the piston engine and only 30% more than the original jet engine.

Graphics by Zane R Nobbs based on CTA drawing

Upon completion the Heliconair HC-II Convertiplano was capable of speeds up to 500 km/h as well as almost direct vertical takeoffs and landings. After testing was completed Dr. Focke returned to Germany and the aircraft was put into storage and virtually forgotten. It remains an almost unknown aircraft outside of Brazil, at least until now. We at the International Resin Modellers Association felt that this was a good candidate for our IRMA Kit No. 5 CTA Heliconair HC-I Convertiplano! The first IRMA kit is the original Double-Mamba version.

Photograph supplied by Comando-Geral de Tecnologia Aerospacial - CTA

For finishing your HC-II kit the following colors are recommended based on research and likelihood of accuracy. From photographs the HC-I appears to be one color on the topside which could range from olive green to dark green. Based on Brazilian Air Force colors, bamboo green would appear to be the most likely. The underside may have also been the same color or possibly a very light gray to a very light sky blue.

Photograph supplied by Comando-Geral de Tecnologia Aerospacial - CTA

Markings are the Brazilian Star, which is five points divided into two halves each. The left side of each point is a light green with the right side a gold yellow. In the center is a blue disk with a white band. The tail rudder was evenly split between the same shades of green at the front with yellow at the back. Later a tail flash in the same colors replaced the rudder colors. All shades match the flag of Brazil.

Photograph supplied by Comando-Geral de Tecnologia Aerospacial - CTA

The majority of photographs in this article are of the CTA Heliconair HC-I Convertiplano in transition to the HC-Ib. Originally designed for the Armstrong Siddeley ASMD 4 Double Mamba turbojet, the Wright R-3350-DA3 Turbo Compound 18-cylinder supercharged radial engine was inserted for testing then removed from the fuselage (in the photos), four General Electric G.E. T-58 gas-turbine jet engines were to be installed on the lift-planes for the HC-II version.

Comando-Geral de Technologica Aerospacial - CTA Photograph

IRMA also wishes to thank Ms. Laurelene Ferraz and Ms. Sônia Leite of the Comando-Geral de Tecnologia Aerospacial - CTA (Brazilian Command for Aerospace Technology) for help in obtaining historic documents, photographs and data to make a kit possible! Also to Mr. Daniel Uhr for help in artistic renditions for research and Ms. Simona Macelaru for design of the kit master.

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